Simple and flexible firewall for Linux server
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#!/bin/sh
# minifirewall is shellscripts for easy firewalling on a standalone server
# we used netfilter/iptables http://netfilter.org/ designed for recent Linux kernel
# See https://gitea.evolix.org/evolix/minifirewall
# Copyright (c) 2007-2020 Evolix
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 3
# of the License.
# Description
# script for standalone server
# Start or stop minifirewall
#
### BEGIN INIT INFO
# Provides: minfirewall
# Required-Start:
# Required-Stop:
# Should-Start: $network $syslog $named
# Should-Stop: $syslog
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: start and stop the firewall
# Description: Firewall designed for standalone server
### END INIT INFO
DESC="minifirewall"
NAME="minifirewall"
# Variables configuration
#########################
# iptables paths
IPT=/sbin/iptables
IPT6=/sbin/ip6tables
# TCP/IP variables
LOOPBACK='127.0.0.0/8'
CLASSA='10.0.0.0/8'
CLASSB='172.16.0.0/12'
CLASSC='192.168.0.0/16'
CLASSD='224.0.0.0/4'
CLASSE='240.0.0.0/5'
ALL='0.0.0.0'
BROAD='255.255.255.255'
PORTSROOT='0:1023'
PORTSUSER='1024:65535'
chain_exists()
{
local chain_name="$1" ; shift
[ $# -eq 1 ] && local intable="--table $1"
iptables $intable -nL "$chain_name" >/dev/null 2>&1
}
# Configuration
oldconfigfile="/etc/firewall.rc"
configfile="/etc/default/minifirewall"
IPV6=$(grep "IPV6=" /etc/default/minifirewall | awk -F '=' -F "'" '{print $2}')
DOCKER=$(grep "DOCKER=" /etc/default/minifirewall | awk -F '=' -F "'" '{print $2}')
INT=$(grep "INT=" /etc/default/minifirewall | awk -F '=' -F "'" '{print $2}')
case "$1" in
start)
echo "Start IPTables rules..."
# Stop and warn if error!
set -e
trap 'echo "ERROR in minifirewall configuration (fix it now!) or script manipulation (fix yourself)." ' INT TERM EXIT
# sysctl network security settings
##################################
# Don't answer to broadcast pings
echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts
# Ignore bogus ICMP responses
echo 1 > /proc/sys/net/ipv4/icmp_ignore_bogus_error_responses
# Disable Source Routing
for i in /proc/sys/net/ipv4/conf/*/accept_source_route; do
echo 0 > $i
done
# Enable TCP SYN cookies to avoid TCP-SYN-FLOOD attacks
# cf http://cr.yp.to/syncookies.html
echo 1 > /proc/sys/net/ipv4/tcp_syncookies
# Disable ICMP redirects
for i in /proc/sys/net/ipv4/conf/*/accept_redirects; do
echo 0 > $i
done
for i in /proc/sys/net/ipv4/conf/*/send_redirects; do
echo 0 > $i
done
# Enable Reverse Path filtering : verify if responses use same network interface
for i in /proc/sys/net/ipv4/conf/*/rp_filter; do
echo 1 > $i
done
# log des paquets avec adresse incoherente
for i in /proc/sys/net/ipv4/conf/*/log_martians; do
echo 1 > $i
done
# IPTables configuration
########################
$IPT -N LOG_DROP
$IPT -A LOG_DROP -j LOG --log-prefix '[IPTABLES DROP] : '
$IPT -A LOG_DROP -j DROP
$IPT -N LOG_ACCEPT
$IPT -A LOG_ACCEPT -j LOG --log-prefix '[IPTABLES ACCEPT] : '
$IPT -A LOG_ACCEPT -j ACCEPT
if test -f $oldconfigfile; then
echo "$oldconfigfile is deprecated, rename to $configfile" >&2
exit 1
fi
if ! test -f $configfile; then
echo "$configfile does not exist" >&2
exit 1
fi
tmpfile=`mktemp`
. $configfile 2>$tmpfile >&2
if [ -s $tmpfile ]; then
echo "$configfile returns standard or error output (see below). Stopping." >&2
cat $tmpfile
exit 1
fi
rm $tmpfile
# Trusted ip addresses
$IPT -N ONLYTRUSTED
$IPT -A ONLYTRUSTED -j LOG_DROP
for x in $TRUSTEDIPS
do
$IPT -I ONLYTRUSTED -s $x -j ACCEPT
done
# Privilegied ip addresses
# (trusted ip addresses *are* privilegied)
$IPT -N ONLYPRIVILEGIED
$IPT -A ONLYPRIVILEGIED -j ONLYTRUSTED
for x in $PRIVILEGIEDIPS
do
$IPT -I ONLYPRIVILEGIED -s $x -j ACCEPT
done
# Chain for restrictions (blacklist IPs/ranges)
$IPT -N NEEDRESTRICT
# We allow all on loopback interface
$IPT -A INPUT -i lo -j ACCEPT
[ "$IPV6" != "off" ] && $IPT6 -A INPUT -i lo -j ACCEPT
# if OUTPUTDROP
$IPT -A OUTPUT -o lo -j ACCEPT
[ "$IPV6" != "off" ] && $IPT6 -A OUTPUT -o lo -j ACCEPT
# We avoid "martians" packets, typical when W32/Blaster virus
# attacked windowsupdate.com and DNS was changed to 127.0.0.1
# $IPT -t NAT -I PREROUTING -s $LOOPBACK -i ! lo -j DROP
$IPT -A INPUT -s $LOOPBACK ! -i lo -j DROP
if [ "$DOCKER" = "on" ]; then
$IPT -N MINIFW-DOCKER-TRUSTED
$IPT -A MINIFW-DOCKER-TRUSTED -j DROP
$IPT -N MINIFW-DOCKER-PRIVILEGED
$IPT -A MINIFW-DOCKER-PRIVILEGED -j MINIFW-DOCKER-TRUSTED
$IPT -A MINIFW-DOCKER-PRIVILEGED -j RETURN
$IPT -N MINIFW-DOCKER-PUB
$IPT -A MINIFW-DOCKER-PUB -j MINIFW-DOCKER-PRIVILEGED
$IPT -A MINIFW-DOCKER-PUB -j RETURN
# Flush DOCKER-USER if exist, create it if absent
if chain_exists 'DOCKER-USER'; then
$IPT -F DOCKER-USER
else
$IPT -N DOCKER-USER
fi;
# Pipe new connection through MINIFW-DOCKER-PUB
$IPT -A DOCKER-USER -i $INT -m state --state NEW -j MINIFW-DOCKER-PUB
$IPT -A DOCKER-USER -j RETURN
fi
# Local services restrictions
#############################
# Allow services for $INTLAN (local server or local network)
$IPT -A INPUT -s $INTLAN -j ACCEPT
# Enable protection chain for sensible services
for x in $SERVICESTCP1p
do
$IPT -A INPUT -p tcp --dport $x -j NEEDRESTRICT
done
for x in $SERVICESUDP1p
do
$IPT -A INPUT -p udp --dport $x -j NEEDRESTRICT
done
# Public service
for x in $SERVICESTCP1
do
$IPT -A INPUT -p tcp --dport $x -j ACCEPT
[ "$IPV6" != "off" ] && $IPT6 -A INPUT -p tcp --dport $x -j ACCEPT
done
for x in $SERVICESUDP1
do
$IPT -A INPUT -p udp --dport $x -j ACCEPT
[ "$IPV6" != "off" ] && $IPT6 -A INPUT -p udp --dport $x -j ACCEPT
done
# Privilegied services
for x in $SERVICESTCP2
do
$IPT -A INPUT -p tcp --dport $x -j ONLYPRIVILEGIED
done
for x in $SERVICESUDP2
do
$IPT -A INPUT -p udp --dport $x -j ONLYPRIVILEGIED
done
# Private services
for x in $SERVICESTCP3
do
$IPT -A INPUT -p tcp --dport $x -j ONLYTRUSTED
done
for x in $SERVICESUDP3
do
$IPT -A INPUT -p udp --dport $x -j ONLYTRUSTED
done
if [ "$DOCKER" = "on" ]; then
# Public services defined in SERVICESTCP1 & SERVICESUDP1
for dstport in $SERVICESTCP1
do
$IPT -I MINIFW-DOCKER-PUB -p tcp --dport "$dstport" -j RETURN
done
for dstport in $SERVICESUDP1
do
$IPT -I MINIFW-DOCKER-PUB -p udp --dport "$dstport" -j RETURN
done
# Privileged services (accessible from privileged & trusted IPs)
for dstport in $SERVICESTCP2
do
for srcip in $PRIVILEGIEDIPS
do
$IPT -I MINIFW-DOCKER-PRIVILEGED -p tcp -s "$srcip" --dport "$dstport" -j RETURN
done
for srcip in $TRUSTEDIPS
do
$IPT -I MINIFW-DOCKER-PRIVILEGED -p tcp -s "$srcip" --dport "$dstport" -j RETURN
done
done
for dstport in $SERVICESUDP2
do
for srcip in $PRIVILEGIEDIPS
do
$IPT -I MINIFW-DOCKER-PRIVILEGED -p udp -s "$srcip" --dport "$dstport" -j RETURN
done
for srcip in $TRUSTEDIPS
do
$IPT -I MINIFW-DOCKER-PRIVILEGED -p udp -s "$srcip" --dport "$dstport" -j RETURN
done
done
# Trusted services (accessible from trusted IPs)
for dstport in $SERVICESTCP3
do
for srcip in $TRUSTEDIPS
do
$IPT -I MINIFW-DOCKER-TRUSTED -p tcp -s "$srcip" --dport "$dstport" -j RETURN
done
done
for dstport in $SERVICESUDP3
do
for srcip in $TRUSTEDIPS
do
$IPT -I MINIFW-DOCKER-TRUSTED -p udp -s "$srcip" --dport "$dstport" -j RETURN
done
done
fi
# External services
###################
# DNS authorizations
for x in $DNSSERVEURS
do
$IPT -A INPUT -p tcp ! --syn --sport 53 --dport $PORTSUSER -s $x -j ACCEPT
$IPT -A INPUT -p udp --sport 53 --dport $PORTSUSER -s $x -m state --state ESTABLISHED,RELATED -j ACCEPT
$IPT -A OUTPUT -o $INT -p udp -d $x --dport 53 --match state --state NEW -j ACCEPT
done
# HTTP (TCP/80) authorizations
for x in $HTTPSITES
do
$IPT -A INPUT -p tcp ! --syn --sport 80 --dport $PORTSUSER -s $x -j ACCEPT
done
# HTTPS (TCP/443) authorizations
for x in $HTTPSSITES
do
$IPT -A INPUT -p tcp ! --syn --sport 443 --dport $PORTSUSER -s $x -j ACCEPT
done
# FTP (so complex protocol...) authorizations
for x in $FTPSITES
do
# requests on Control connection
$IPT -A INPUT -p tcp ! --syn --sport 21 --dport $PORTSUSER -s $x -j ACCEPT
# FTP port-mode on Data Connection
$IPT -A INPUT -p tcp --sport 20 --dport $PORTSUSER -s $x -j ACCEPT
# FTP passive-mode on Data Connection
# WARNING, this allow all connections on TCP ports > 1024
$IPT -A INPUT -p tcp ! --syn --sport $PORTSUSER --dport $PORTSUSER -s $x -j ACCEPT
done
# SSH authorizations
for x in $SSHOK
do
$IPT -A INPUT -p tcp ! --syn --sport 22 -s $x -j ACCEPT
done
# SMTP authorizations
for x in $SMTPOK
do
$IPT -A INPUT -p tcp ! --syn --sport 25 --dport $PORTSUSER -s $x -j ACCEPT
done
# secure SMTP (TCP/465 et TCP/587) authorizations
for x in $SMTPSECUREOK
do
$IPT -A INPUT -p tcp ! --syn --sport 465 --dport $PORTSUSER -s $x -j ACCEPT
$IPT -A INPUT -p tcp ! --syn --sport 587 --dport $PORTSUSER -s $x -j ACCEPT
done
# NTP authorizations
for x in $NTPOK
do
$IPT -A INPUT -p udp --sport 123 -s $x -j ACCEPT
$IPT -A OUTPUT -o $INT -p udp -d $x --dport 123 --match state --state NEW -j ACCEPT
done
# Always allow ICMP
$IPT -A INPUT -p icmp -j ACCEPT
[ "$IPV6" != "off" ] && $IPT6 -A INPUT -p icmpv6 -j ACCEPT
# IPTables policy
#################
# by default DROP INPUT packets
$IPT -P INPUT DROP
[ "$IPV6" != "off" ] && $IPT6 -P INPUT DROP
# by default, no FORWARING (deprecated for Virtual Machines)
#echo 0 > /proc/sys/net/ipv4/ip_forward
#$IPT -P FORWARD DROP
#$IPT6 -P FORWARD DROP
# by default allow OUTPUT packets... but drop UDP packets (see OUTPUTDROP to drop OUTPUT packets)
$IPT -P OUTPUT ACCEPT
[ "$IPV6" != "off" ] && $IPT6 -P OUTPUT ACCEPT
$IPT -A OUTPUT -o $INT -p udp --dport 33434:33523 --match state --state NEW -j ACCEPT
$IPT -A OUTPUT -p udp --match state --state ESTABLISHED,RELATED -j ACCEPT
$IPT -A OUTPUT -p udp -j DROP
[ "$IPV6" != "off" ] && $IPT6 -A OUTPUT -o $INT -p udp --dport 33434:33523 --match state --state NEW -j ACCEPT
[ "$IPV6" != "off" ] && $IPT6 -A OUTPUT -p udp --match state --state ESTABLISHED,RELATED -j ACCEPT
[ "$IPV6" != "off" ] && $IPT6 -A OUTPUT -p udp -j DROP
trap - INT TERM EXIT
echo "...starting IPTables rules is now finish : OK"
;;
stop)
echo "Flush all rules and accept everything..."
# Delete all rules
$IPT -F INPUT
$IPT -F OUTPUT
$IPT -F LOG_DROP
$IPT -F LOG_ACCEPT
$IPT -F ONLYTRUSTED
$IPT -F ONLYPRIVILEGIED
$IPT -F NEEDRESTRICT
[ "$DOCKER" = "off" ] && $IPT -t nat -F
$IPT -t mangle -F
[ "$IPV6" != "off" ] && $IPT6 -F INPUT
[ "$IPV6" != "off" ] && $IPT6 -F OUTPUT
if [ "$DOCKER" = "on" ]; then
$IPT -F DOCKER-USER
$IPT -A DOCKER-USER -j RETURN
$IPT -F MINIFW-DOCKER-PUB
$IPT -X MINIFW-DOCKER-PUB
$IPT -F MINIFW-DOCKER-PRIVILEGED
$IPT -X MINIFW-DOCKER-PRIVILEGED
$IPT -F MINIFW-DOCKER-TRUSTED
$IPT -X MINIFW-DOCKER-TRUSTED
fi
# Accept all
$IPT -P INPUT ACCEPT
$IPT -P OUTPUT ACCEPT
[ "$IPV6" != "off" ] && $IPT6 -P INPUT ACCEPT
[ "$IPV6" != "off" ] && $IPT6 -P OUTPUT ACCEPT
#$IPT -P FORWARD ACCEPT
#$IPT -t nat -P PREROUTING ACCEPT
#$IPT -t nat -P POSTROUTING ACCEPT
# Delete non-standard chains
$IPT -X LOG_DROP
$IPT -X LOG_ACCEPT
$IPT -X ONLYPRIVILEGIED
$IPT -X ONLYTRUSTED
$IPT -X NEEDRESTRICT
echo "...flushing IPTables rules is now finish : OK"
;;
status)
$IPT -L -n -v --line-numbers
$IPT -t nat -L -n -v --line-numbers
$IPT -t mangle -L -n -v --line-numbers
$IPT6 -L -n -v --line-numbers
$IPT6 -t mangle -L -n -v --line-numbers
;;
reset)
echo "Reset all IPTables counters..."
$IPT -Z
$IPT -t nat -Z
$IPT -t mangle -Z
[ "$IPV6" != "off" ] && $IPT6 -Z
[ "$IPV6" != "off" ] && $IPT6 -t mangle -Z
echo "...reseting IPTables counters is now finish : OK"
;;
restart)
$0 stop
$0 start
;;
*)
echo "Usage: $0 {start|stop|restart|status|reset|squid}"
exit 1
esac
exit 0